CN112691495B - Method for treating waste gas generated in synthetic leather production process - Google Patents
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- B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
- B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
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- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1412—Controlling the absorption process
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- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/18—Absorbing units; Liquid distributors therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D2252/00—Absorbents, i.e. solvents and liquid materials for gas absorption
- B01D2252/10—Inorganic absorbents
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- B01D2253/10—Inorganic adsorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D2259/00—Type of treatment
- B01D2259/40—Further details for adsorption processes and devices
- B01D2259/40083—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption
- B01D2259/40086—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption by using a purge gas
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- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Abstract
A method for treating waste gas in the production process of synthetic leather comprises the steps of firstly spraying and washing 4 sections of circulating waste gas absorption, and firstly cooling, condensing and then freezing; firstly spraying and washing 4-section circulating waste gas absorption, collecting the waste gas in a centralized way, collecting the mixed waste gas at 90-110 ℃ generated in the synthetic leather processing technology in a centralized way, and collecting the gas concentration in a centralized way to reach 4900-5100mg/m3The DMF in the mixed waste gas component accounts for 4400-4600mg/m3The other waste gas components account for 400-600mg/m3(ii) a The concentration of the collected mixed waste gas reaches 5000mg/m3And then, filtering the mixed waste gas by a reverse osmosis membrane filter screen to remove partial solids and sticky substances, and then cooling and condensing and then freezing the mixed waste gas by matching with a cooling tower, wherein the cooling and condensing and then freezing treatment comprises cooling and condensing treatment and freezing treatment, and the cooling and condensing treatment is to condense the waste gas by using an external spray cooler to obtain high-concentration waste liquid with the concentration of 70-80% and the temperature of 40-50 ℃.
Description
Technical Field
The invention relates to the field of environmental protection, in particular to a method for treating waste gas generated in the production process of synthetic leather.
Background
The PU resin used in the production process of the synthetic leather is dissolved in an organic solvent, the solvent mainly comprises DMF (N, N-dimethylformamide), toluene and butanone, the DMF is washed in water in wet production, the DMF is volatilized into hot air of an oven in dry production, and if the washing water in the wet production and the hot air in the dry production are directly discharged, the DMF is wasted and the environment is polluted. At present, DMF waste water of wet process production line has been retrieved basically, when environmental protection, also for can increasing economic benefits with waste gas recycle, hot-blast that the dry process production line discharged has also basically been collected, administered, waste gas in the synthetic leather dry process production process mainly has DMF, toluene, butanone, wherein DMF's content is higher, and waste gas concentration reaches 5000mg/m and washes by the year usually, and wherein DMF about 4500mg/m washes by the year, and other solvent components account for about 500mg/m washes by the year.
At present, the basic method for waste gas absorption in the dry production process of synthetic leather production is mainly DMF absorption tower collection, but the method for collecting by using the DMF absorption tower can only be used for collecting DMF waste gas, the treatment method of other waste gas after collecting the DMF waste gas at the present stage is troublesome, the wettability of the filler is low under the working condition of very low liquid distribution density, the absorption efficiency of the filler tower is low, no method for ensuring high wettability of the filler and improving the absorption efficiency and simultaneously reducing the distillation load and cost of waste liquid is provided, the problems of complex process flow, incomplete filler cleaning of sticky substances, large water consumption and waste liquid external discharge capacity, high distilled water cost and the like exist in the process of absorbing the DMF waste gas, other component waste gas exists besides DMF, if only DMF recovery is considered in the production process, other waste gas is excessively discharged and cannot meet the environmental protection requirement, further processing is required.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provides a method capable of fully recovering DMF and other waste gases.
The invention adopts the technical scheme for solving the technical problems that: the method for treating the waste gas in the synthetic leather production process comprises the steps of firstly spraying and washing 4-section circulating waste gas absorption, and firstly cooling, condensing and then freezing;
the method comprises the following main steps of firstly spraying and washing 4 sections of circulating waste gas absorption:
step 1, collecting waste gas in a centralized manner, namely collecting the mixed waste gas at 90-110 ℃ generated in the synthetic leather processing technology in a centralized manner, carrying out topdressing when the concentration of the collected gas reaches 4900. quadrature. 5100mg/m, wherein DMF accounts for 4400. quadrature. 4600mg/m in the components of the mixed waste gas during the flowering from top to bottom, and other waste gas components account for 400. quadrature. 600 mg/m;
step 2, after the mixed waste gas is collected and formed in the step 1 and the concentration of the mixed waste gas reaches 5000mg/m, filtering the mixed waste gas through a reverse osmosis membrane filter screen to remove partial solids and sticky substances, and then cooling, condensing and freezing the mixed waste gas in a cooling tower, wherein the cooling, condensing and freezing treatment comprises cooling, condensing and freezing treatment, and the cooling, condensing the waste gas by using an external spray cooler to obtain high-concentration waste liquid with the concentration of 70-80% and the temperature of 40-50 ℃;
step 3, after the high-concentration waste liquid is formed in the step 2, entering a freezing treatment stage, wherein the freezing treatment is in a form that an evaporator and a circulating liquid cooler of a refrigerator are used together, the high-concentration waste liquid is introduced into the refrigerator, meanwhile, a circulating spray pump is used for recycling type pressurized spray washing, the high-concentration waste liquid is subjected to solid and sticky substance removal treatment, the characteristic of strong DMF water solubility is utilized, DMF waste gas in the waste liquid is preliminarily absorbed and filtered, and cooling waste gas with the temperature of 25-35 ℃ is formed after the freezing treatment;
step 4, after the step 3, introducing cooling waste gas from the bottom end of the filler absorption tower, performing 4-section circulating filler spraying on the introduced cooling waste gas to remove solids, sticky substances and DMF, and introducing the cooling waste gas into the tower top to form tower top waste gas;
and 5, carrying out catalytic treatment on the tower top waste gas in the step 4 by using a catalyst to reduce the VOC concentration, obtaining high-temperature waste gas at the temperature of 180-210 ℃ after the catalytic treatment, and introducing the high-temperature waste gas into an adsorption concentrator for continuous desorption to reach the emission standard.
For further improvement, the external spray cooler in the step 2 of the 4-section circulating waste gas absorption treatment of the first spray washing is a large-scale external water film evaporation condenser, the specification of the heat exchange surface of the cooler is 350-380 square meters, the power of the cooling fan is 3kw, the material is 304/glass fiber reinforced plastic, the purpose of the first cooling and condensing treatment is to reduce the treatment difficulty by considering the subsequent treatment method of the adsorption concentrator through a plate, the temperature of the waste gas at the top of the tower is up to 37 ℃ without the first cooling and condensing treatment and then cooling treatment, the relative humidity is up to 95%, even if the hydrophobic zeolite concentration rotating wheel is adopted, the purification efficiency is only 80%, the activated carbon fiber concentrator is possibly lower, and at the moment, if the temperature is reduced to 35 ℃ and the relative humidity is reduced to 50%, an ideal refrigeration dehumidifier is adopted for treatment, although the absorption temperature is reduced by the evaporation of a large amount of water in the absorption process, however, evaporation of a large amount of water increases humidity, which makes subsequent treatment difficult and increases cost, and therefore, a cooling condensation treatment is preferentially performed to obtain a high-concentration waste liquid.
Further perfecting, the treatment efficiency of the cooling tower in the step 2 of the 4-section circulating waste gas absorption treatment of the first spraying washing is 20-50 t/h.
Further perfection, the power of the refrigerator in the 4-stage circulation waste gas absorption treatment step 3 of the first spraying washing is 18.5-55kw, the cooling fan with the wind pressure 3800-4000Pa, the wind rate 33000-100000 m/h and the power of 55-160kw is used for further cooling the formed high-concentration waste liquid, and the temperature of the waste gas introduced to the bottom of the filler absorption tower is reduced to 28-30 ℃.
Further perfection, the power of the circulating spray pump in the step 3 of the 4-section circulating waste gas absorption treatment of the first spraying washing is 5.5-15kw, the circulating spray pump and the refrigerating machine work together, and the circulating spray pump reduces the temperature of the high-concentration waste liquid, so that most of solids and sticky substances are removed from the high-concentration waste liquid before the high-concentration waste liquid enters the filler absorption tower, and part of DMF is absorbed, and the waste gas treatment efficiency is improved.
Further perfecting, the filler absorption tower in the step 4 of the 4-section circulating waste gas absorption treatment of the first spraying washing is a 4-section circulating filler pure water pure countercurrent absorption tower, and the diameter is 3.8 m;
the use method of the packing absorption tower comprises the steps that the upper section of the packing is adopted, a circulating spray pump sprays pure water or distilled water downwards from the top end, cooling waste gas is introduced into the lower section of the packing, the cooling waste gas is mixed and absorbed with the pure water and the packing from bottom to top, absorbed absorption liquid drops into the bottom of the tower to form tower bottom liquid, the tower bottom liquid is mixed liquid formed by mixing water and DMF, the concentration of the DMF is 14-18%, 3 sections of circulation is generally adopted, and the emission concentration of the tower bottom liquid is 10-15% under the condition that the DMF component of the waste gas discharged from the top of the tower is up to the standard.
Further perfection, the adsorption concentrator in the step 5 of the 4-section cyclic waste gas absorption treatment of firstly spraying and washing is an activated carbon fiber adsorption concentrator, the power of a desorption fan of the adsorption concentrator is 5.5-11kw, the air pressure is 2500 + 3000Pa, and the air volume is 3600 + 3800m and the top of the tower/h is cooled and condensed before the adsorption concentrator is carried out, and then the adsorption is concentrated and adsorbed by the activated carbon fiber adsorption concentrator when the tower top waste gas is formed, so that the adsorption difficulty is reduced, and the adsorption cost is saved at the same time.
Further perfecting, the recovery type pressurized spraying washing in the step 3 of the 4-section circulating waste gas absorption treatment of the first spraying washing is carried out, and the operation method comprises the steps of pumping a part of mixed liquid with the DMF concentration of 14-18% obtained at the bottom of the tower to a circulating spraying pump at the top end of a filler absorption tower through circulating water for downward spraying; pressurizing the mixed solution by the other part of the mixed solution through a circulating water pump, sending the pressurized mixed solution to a circulating spray pump in a refrigerator for cooling, spraying and absorbing high-concentration waste liquid, wherein the DMF concentration of the cooled, sprayed and absorbed mixed solution is 24-26%, and if the same recovery efficiency is realized, the discharge concentration of the bottom liquid of the 4-section circulating spray tower is 14-18%, if the same recovery efficiency is adopted; the other part of the mixed liquor is pressurized by a circulating water pump, and the concentration of DMF of the mixed liquor at the bottom of circulating spraying can reach 24-26 percent, so that the absorption rate of distilled water is improved.
The power of the circulating water pump is 5.5-15kw, the concentration of the waste liquid can be improved from 15% to 25% after circulating absorption by the circulating water pump, if 3 tons of DMF are recycled, the total amount of the discharged waste liquid is reduced from 20 tons to 12 tons, the cost of distilled water is greatly reduced, and the cost of distilled water is saved.
The invention has the beneficial effects that: the absorption process of the invention has the following advantages:
firstly, the process flow is simple, the circulating spraying and the first-stage filling absorption are added, and by utilizing the characteristic of very good water solubility of DMF, the absorption liquid at the bottom of the filling tower is pressurized by a circulating pump, and the first-stage recovery type pressurized spraying washing is firstly carried out before the waste gas enters the filling absorption tower;
the spraying strength of the pressurized absorption liquid is high, sticky substances in the waste gas are removed more thoroughly, the difficulty in cleaning the filler is reduced, the relative humidity of the waste gas is improved, the waste gas entering the filler absorption tower at the later stage can wet the filler from the lower end, and the wetting degree of the filler is high;
the water consumption and the waste liquid discharge capacity are reduced, and the distillation cost of discharged waste liquid is reduced;
the DMF component treatment process of firstly cooling and condensing and then freezing and absorbing is adopted, and the treated waste gas is subjected to adsorption concentration treatment, so that the DMF absorption efficiency is improved, the distillation cost is reduced, and the efficiency of subsequently adopting adsorption concentration on other waste gases is not influenced;
cooling, condensing and freezing the waste gas, and then expanding with heat and contracting with cold to increase the density of the waste gas and adjust the waste gas to reach the optimal gas phase load.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings in which:
with reference to the accompanying drawings: the method for treating the waste gas in the synthetic leather production process comprises the steps of firstly spraying and washing 4-section circulating waste gas absorption, and firstly cooling, condensing and then freezing;
the method comprises the following main steps of firstly spraying and washing 4 sections of circulating waste gas absorption:
step 1, collecting waste gas in a centralized manner, namely collecting the mixed waste gas at 90-110 ℃ generated in the synthetic leather processing technology in a centralized manner, carrying out topdressing when the concentration of the collected gas reaches 4900. quadrature. 5100mg/m, wherein DMF accounts for 4400. quadrature. 4600mg/m in the components of the mixed waste gas during the flowering from top to bottom, and other waste gas components account for 400. quadrature. 600 mg/m;
step 2, after the mixed waste gas is collected and formed in the step 1 and the concentration of the mixed waste gas reaches 5000mg/m, filtering the mixed waste gas through a reverse osmosis membrane filter screen to remove partial solids and sticky substances, and then cooling, condensing and freezing the mixed waste gas in a cooling tower, wherein the cooling, condensing and freezing treatment comprises cooling, condensing and freezing treatment, and the cooling, condensing the waste gas by using an external spray cooler to obtain high-concentration waste liquid with the concentration of 70-80% and the temperature of 40-50 ℃;
step 3, after the high-concentration waste liquid is formed in the step 2, entering a freezing treatment stage, wherein the freezing treatment is in a form that an evaporator and a circulating liquid cooler of a refrigerator are used together, the high-concentration waste liquid is introduced into the refrigerator, meanwhile, a circulating spray pump is used for recycling type pressurized spray washing, the high-concentration waste liquid is subjected to solid and sticky substance removal treatment, the characteristic of strong DMF water solubility is utilized, DMF waste gas in the waste liquid is preliminarily absorbed and filtered, and cooling waste gas with the temperature of 25-35 ℃ is formed after the freezing treatment;
step 4, after the step 3, introducing cooling waste gas from the bottom end of the filler absorption tower, performing 4-section circulating filler spraying on the introduced cooling waste gas to remove solids, sticky substances and DMF, and introducing the cooling waste gas into the tower top to form tower top waste gas;
and 5, carrying out catalytic treatment on the tower top waste gas in the step 4 by using a catalyst to reduce the VOC concentration, obtaining high-temperature waste gas at the temperature of 180-210 ℃ after the catalytic treatment, and introducing the high-temperature waste gas into an adsorption concentrator for continuous desorption to reach the emission standard.
The external pipe spray cooler in the step 2 of the first spray washing 4-section circulating waste gas absorption treatment is a large-scale external pipe water film evaporation condenser, the specification of the heat exchange surface of the cooler is 350-inch square meter and 380-inch square meter, the power of the cooling fan is 3kw, and the material is 304/glass fiber reinforced plastic.
The treatment efficiency of the cooling tower in the step 2 of the absorption treatment of the waste gas with the first-stage circulation of spraying and washing is 20-50 t/h.
The power of the refrigerator in the step 3 of the first-spraying-washing 4-section circulating waste gas absorption treatment is 18.5-55kw, and the cooling fan with the wind pressure of 3800 and 4000Pa, the wind rate of 33000 and 100000m for carrying out cultivation/h and the power of 55-160kw is adopted.
The power of the circulating spray pump in the step 3 of the absorption treatment of the waste gas which is firstly sprayed and washed and circulated in the 4 sections is 5.5-15 kw.
The filler absorption tower in the step 4 of the first-stage spray washing 4-section circulating waste gas absorption treatment is a 4-section circulating filler pure water pure countercurrent absorption tower, and the diameter of the tower is 3.8 m;
the use method of the filler absorption tower comprises the steps that the upper section of the filler is filled, pure water or distilled water is sprayed downwards from the top end by a circulating spray pump, cooling waste gas is introduced into the lower section of the filler, the cooling waste gas is mixed with the pure water and the filler from bottom to top for absorption, the absorbed absorption liquid drops into the bottom of the tower to form tower bottom liquid, the tower bottom liquid is mixed liquid formed by mixing water and DMF, and the concentration of the DMF is 14-18%.
The adsorption concentrator in the 4-stage cycle waste gas absorption treatment step 5 of first spray washing is an activated carbon fiber adsorption concentrator, the power of a desorption fan of the adsorption concentrator is 5.5-11kw, the air pressure is 2500-.
The operation method of the recovery type pressurized spraying washing in the step 3 of the 4-section circulating waste gas absorption treatment of the first spraying washing comprises the steps of pumping a part of mixed solution with the DMF concentration of 14-18% obtained at the bottom of the tower to a circulating spraying pump at the top end of the filler absorption tower through circulating water for downward spraying; and pressurizing the other part of the mixed solution by a circulating water pump, sending the pressurized mixed solution to a circulating spray pump in a refrigerator for cooling, spraying and absorbing high-concentration waste liquid, wherein the DMF concentration of the cooled, sprayed and absorbed mixed solution is 24-26%.
The power of the circulating water pump is 5.5-15 kw.
Example 1
Taking single line for carrying out fruit and vegetable cultivation under 40000m, carrying out fruit and vegetable cultivation at 100 ℃, 4500mg/m, carrying out fruit and vegetable cultivation at 500mg/m on DMF by taking the steps as examples, carrying out fruit and vegetable cultivation under freezing spray circulation liquid outlet temperature according to 27 ℃, carrying out fruit and vegetable cultivation under refrigeration coefficient according to 8, carrying out fruit and vegetable cultivation under waste gas standard state gas quantity according to 29276m, carrying out cooling condensation load according to Q =550000kcal/h, carrying out heat exchange on a cooler by about 350 square meters, carrying out cooling on a cooling fan by 3kw, carrying out a circulating water pump by 5.5kw, carrying out freezing load by 100000kcal/h, allocating a 20t/h cooling tower, carrying out refrigerator power by 18.5kw, carrying out fan wind pressure by 4000Pa, carrying out wind volume by 33000 m/h, carrying out power by 55kw, carrying out circulating spray pump by 5.5kw, desorbing fan by 2500Pa, carrying out fruit and vegetable cultivation at 3600 m/h, carrying out fruit and vegetable cultivation under power by 5.5kw, carrying out fruit and fruit cultivation under refrigeration by taking the fruit and vegetable cultivation under refrigeration by year, carrying out fruit and fruit cultivation under refrigeration by taking the year by year, carrying out cultivation under refrigeration by year after 40000 and year, wherein the year after year, and year, wherein the year after year, which year after year, which is 40000, and year after year, wherein the year after year, wherein the year after year, and year after year, wherein the year, which is 40000 and year, and when year after year, and when year after year, and year after year, wherein the year after year, and when year after year, and year after year, and when the year after.
The cooling condenser adopts a large-scale external membrane evaporation condenser, a reasonable water distribution structure is needed in order to increase the water evaporation cooling effect, a forced convection axial flow fan is also needed to increase the cooling air speed, a DMF absorption tower is the core equipment of a DMF absorption process, the reasonable design of the DMF absorption tower directly influences the DMF absorption effect, the lower end of the tower adopts circulating freezing spraying, circulating liquid is subjected to freezing and temperature reduction treatment, and a high-efficiency spray head specially developed by Zhejiang Jinchao industry Co., Ltd is adopted to ensure the purification effect and the distribution uniformity of the spraying liquid; the upper end adopts high-efficiency regular corrugated packing with large specific surface area, high porosity and small pressure drop, and adopts high-precision water distribution pure countercurrent absorption technology to provide maximum absorption driving force, improve absorption efficiency and improve waste liquid concentration. The adsorption concentrator adopts an active carbon fiber continuous adsorption desorption concentrator, which has higher resistance but higher investment, material replacement cost and safety compared with a zeolite honeycomb rotating wheel concentrator. The catalytic converter is a noble metal catalyst which is started by adopting electric heating and has a honeycomb ceramic carrier for a catalytic oxidation device. While the water tubes arranged in the catalytic bed draw off the excess heat. The specific equipment is shown in the following table:
TABLE 1 DMF waste gas recovery device equipment table
Example 2
In the general chemical absorption process, pure absorbent is added into the tower top through a liquid distributor to perform pure countercurrent mass transfer absorption with waste gas, so that the maximum driving force of mass transfer absorption (effective maximum mass transfer concentration difference) exists, but because the DMF has very good water solubility, the water consumption of the dry synthetic leather waste gas absorption packed tower is very small, the very poor wettability of packing materials at such small water distribution quantities (0.15 m/square meter h) can also affect the absorption efficiency, so that the currently used dry process absorption towers adopt 3 or 4 sections of circulation process, although the absorption liquid circulation destroys part of absorption mass transfer concentration difference, the wettability of the filler can be ensured, the absorption effect can also be ensured, usually 3 sections of circulation, under the working condition of ensuring that DMF components of waste gas discharged from the top of the tower reach the standard, the discharge concentration of the bottom liquid of the tower can reach 10-15%, and the discharge concentration of the bottom liquid of the tower can reach 14-18% by adopting 4-section circulation. Theoretically, the maximum effective concentration difference of pure water entering the tower top for pure countercurrent absorption mass transfer can be achieved only by infinite circulation. The absorption process with the maximum effective mass transfer concentration difference of pure water countercurrent absorption of single-section packing is developed by Zhejiang Jinchao industry Co., Ltd, and the combination of gas phase load, high-precision liquid distribution and high-wetting packing technology is optimized, so that the wettability of the packing can be still ensured under the working condition of very low liquid distribution density, the packed tower can play a role in higher absorption efficiency, the dry absorption tower adopting the technology can reach the same tower top discharge concentration, the tower bottom discharge concentration can reach about 25%, and the distillation load and cost of waste liquid are greatly reduced.
TABLE 2 comparison table of discharge concentration of pure water counter-current absorption tower bottoms with single-stage packing
Whether the circulating spraying is added or not in table 2 is to add a section of spraying before the waste gas enters the absorption tower and then discharge the absorption liquid by partially circulating spraying the absorption liquid of the absorption tower, namely the mixed liquid mentioned in claim 8.
Example 3
In the above example 2, only the recovery of DMF is considered, if 5000mg/m of waste gas is preferentially collected, most of DMF is removed in 1600mg/m of thin film fruit trees at 4400, other harmful solvent components at about 500mg/m still exist, and the emission standard is far from being met, further treatment is required, but if only 3 or 4 stages of circulation of the dry absorption tower are adopted, the temperature of the waste gas reaching the top of the tower is as high as 37 ℃, the relative humidity is as high as 95%, the subsequent adsorption concentration efficiency is influenced to a certain extent, even if the hydrophobic zeolite concentration wheel is adopted, the purification efficiency is 60-70%, and the cost of the method is too high; if the concentrator adopting the activated carbon fiber with lower cost has the efficiency of only 50-60 percent; if the temperature is reduced to 35 ℃ and the relative humidity is reduced to about 50%, a refrigeration dehumidifier is needed for treatment, although the absorption temperature is reduced by the evaporation of a large amount of water in the absorption process, the subsequent treatment is difficult because the humidity is increased by the evaporation of the large amount of water; therefore, the treatment process needs to be considered, the DMF component treatment process of firstly cooling and condensing and then freezing and absorbing is adopted, and the treated waste gas is subjected to adsorption and concentration treatment to reach the emission standard.
TABLE 3 comparison table of cooling, condensing and freezing treatment
In table 3, the temperature at the bottom of the tower is the temperature of the waste gas just entering the tower opening at the bottom end of the absorption tower, the temperature at the top of the tower is the temperature of the waste gas after the filler of the absorption tower is sprayed in a countercurrent mode, and the purification efficiency is the purification efficiency of further processing the waste gas at the top of the tower.
In conclusion, the treatment method of cooling and condensing before entering the absorption tower and performing freezing cyclic spraying after cooling can increase the concentration of the gas entering the tower bottom to improve the absorption efficiency, and can also reduce the difficulty of further processing other waste gas in the later period to improve the purification efficiency of purifying other gases in the embodiment 3.
While the invention has been shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the appended claims.
Claims (9)
1. A method for treating waste gas generated in the production process of synthetic leather is characterized by comprising the following steps: comprises the steps of firstly spraying and washing 4-section circulating waste gas absorption and firstly cooling and condensing and then freezing treatment;
the method comprises the following main steps of firstly spraying and washing 4 sections of circulating waste gas absorption:
step 1, collecting waste gas in a centralized manner, namely collecting the mixed waste gas at 90-110 ℃ generated in the synthetic leather processing technology in a centralized manner, carrying out topdressing when the concentration of the collected gas reaches 4900. quadrature. 5100mg/m, wherein DMF accounts for 4400. quadrature. 4600mg/m in the components of the mixed waste gas during the flowering from top to bottom, and other waste gas components account for 400. quadrature. 600 mg/m;
step 2, after the mixed waste gas is collected and formed in the step 1 and the concentration of the mixed waste gas reaches 5000mg/m, filtering the mixed waste gas through a reverse osmosis membrane filter screen to remove partial solids and sticky substances, and then cooling, condensing and freezing the mixed waste gas in a cooling tower, wherein the cooling, condensing and freezing treatment comprises cooling, condensing and freezing treatment, and the cooling, condensing the waste gas by using an external spray cooler to obtain high-concentration waste liquid with the concentration of 70-80% and the temperature of 40-50 ℃;
step 3, after the high-concentration waste liquid is formed in the step 2, entering a freezing treatment stage, wherein the freezing treatment is in a form that an evaporator and a circulating liquid cooler of a refrigerator are used together, the high-concentration waste liquid is introduced into the refrigerator, meanwhile, a circulating spray pump is used for recycling type pressurized spray washing, the high-concentration waste liquid is subjected to solid and sticky substance removal treatment, the characteristic of strong DMF water solubility is utilized, DMF waste gas in the waste liquid is preliminarily absorbed and filtered, and cooling waste gas with the temperature of 25-35 ℃ is formed after the freezing treatment;
step 4, after the step 3, introducing cooling waste gas from the bottom end of the filler absorption tower, performing 4-stage circulating filler spraying on the introduced cooling waste gas to remove solids, sticky matters and DMF (dimethyl formamide), and introducing the cooling waste gas into the tower top to form tower top waste gas;
and 5, carrying out catalytic treatment on the tower top waste gas in the step 4 by using a catalyst to reduce the VOC concentration, obtaining high-temperature waste gas at the temperature of 180-210 ℃ after the catalytic treatment, and introducing the high-temperature waste gas into an adsorption concentrator for continuous desorption to reach the emission standard.
2. The method for treating waste gas generated in the synthetic leather production process according to claim 1, which is characterized by comprising the following steps of: the external pipe spray cooler in the step 2 of the first spray washing 4-section circulating waste gas absorption treatment is a large-scale external pipe water film evaporation condenser, the specification of the heat exchange surface of the cooler is 350-inch square meter and 380-inch square meter, the power of the cooling fan is 3kw, and the material is 304/glass fiber reinforced plastic.
3. The method for treating waste gas generated in the synthetic leather production process according to claim 1, which is characterized by comprising the following steps of: the treatment efficiency of the cooling tower in the step 2 of the absorption treatment of the waste gas which is washed by spraying first and circulated in 4 sections is 20-50 t/h.
4. The method for treating waste gas generated in the synthetic leather production process according to claim 1, which is characterized by comprising the following steps of: the power of the refrigerator in the step 3 of the 4-stage circular waste gas absorption treatment of the first spraying and washing is 18.5-55kw, and the cooling fan with the wind pressure of 3800 and 4000Pa, the wind rate of 33000 and 100000m for transportation/h and the power of 55-160kw is adopted.
5. The method for treating waste gas generated in the synthetic leather production process according to claim 1, which is characterized by comprising the following steps of: the power of the circulating spray pump in the step 3 of the absorption treatment of the waste gas which is firstly sprayed and washed and circulated in the 4 sections is 5.5-15 kw.
6. The method for treating waste gas generated in the synthetic leather production process according to claim 1, which is characterized by comprising the following steps of: the filler absorption tower in the 4-section circulating waste gas absorption treatment step 4 which is sprayed and washed firstly is a 4-section circulating filler pure water pure countercurrent absorption tower, and the diameter of the filler absorption tower is 3.8 m;
the use method of the filler absorption tower comprises the steps that the upper section of the filler is filled, pure water or distilled water is sprayed downwards from the top end by a circulating spray pump, cooling waste gas is introduced into the lower section of the filler, the cooling waste gas is mixed with the pure water and the filler from bottom to top for absorption, the absorbed absorption liquid drops into the bottom of the tower to form tower bottom liquid, the tower bottom liquid is mixed liquid formed by mixing water and DMF, and the concentration of the DMF is 14-18%.
7. The method for treating waste gas generated in the synthetic leather production process according to claim 1, which is characterized by comprising the following steps of: the adsorption concentrator in the step 5 of the 4-section cyclic waste gas absorption treatment of the first spraying washing is an activated carbon fiber adsorption concentrator, the power of a desorption fan of the adsorption concentrator is 5.5-11kw, the air pressure is 2500-.
8. The method for treating waste gas generated in the synthetic leather production process according to claim 6, which is characterized by comprising the following steps of: the operation method of the recovery type pressurized spraying washing in the step 3 of the 4-section circulating waste gas absorption treatment of the first spraying washing comprises the steps of pumping a part of mixed solution with the DMF concentration of 14-18% obtained at the bottom of the tower to a circulating spraying pump at the top end of the filler absorption tower through circulating water for downward spraying; and pressurizing the other part of the mixed solution by a circulating water pump, sending the pressurized mixed solution to a circulating spray pump in a refrigerator for cooling, spraying and absorbing high-concentration waste liquid, wherein the DMF concentration of the cooled, sprayed and absorbed mixed solution is 24-26%.
9. The method for treating waste gas generated in the synthetic leather production process according to claim 8, which is characterized by comprising the following steps of: the power of the circulating water pump is 5.5-15 kw.
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